The Marumi DHG Variable Gray Filter is a variable neutral density filter with a diameter of 52 mm. Neutral density filters are available in various strengths, such as ND2 (1 stop), ND4 (2 stops), ND8 (3 stops), and so on. A variable neutral density filter consists of two polarizing filters that are rotated against each other. When both polarizing filters are parallel, the least amount of light is allowed through. When positioned perpendicular to each other, the light is ideally completely blocked. A variable filter can replace a whole range of fixed ND filters, making it more practical to use. By rotating the filter, you can reduce light from ND2 to ND400 (1 to 8 stops).

A neutral density filter is needed, for example:

• To reduce light on a clear day, allowing for a longer shutter speed to capture movements such as flowing water.
• To use a very wide aperture on a clear day, resulting in a very shallow depth of field in a photo.